Essential tremor (ET) is a common tremor which affects men and women, and increases with age. It may affect up to 3.5% of the population over the age of 65 years. There is some evidence that the tremor runs in families. Despite the perception in the neurological community that ET is partly a genetically-determined disorder, the extent of familal aggregation is not known. In other words, to what extent does this disorder run in families? There have been only a few community-based studies of the genetics of ET. Additionally, there are no data linking ET to any specific gene or chromosome. The goal of the present study is to answer two questions: (1) How much does ET run in families? (2) If ET does run in families, is it handed down from generation to generation in any kind of a predictable pattern? We hope that this study will also lay the groundwork to answer a third question, namely, can we link ET to any particular gene chromosome? Four groups of individuals will undergo a single 20-30 minute neurological history and videotaped-examination. These groups are: (1 individuals with ET identified through the Northern Manhattan Aging Project, (2) first-and second-degreee relatives of individuals with ET (first-degree relatives include parents, siblings and children, while second-degree relatives include grandparents, grandchildren, aunts, uncles, nieces, and nephews), (3) aged-matched normal healthy control subjects identified through the Northern Manhattan Aging Project, and (4) first-and second-degree relatives of normal healthy control subjects. After reviewing the neurological history and videotaped-examination, a study neurologist as well as two other neurologists will decide whether or not individuals in the four groups mentioned above may be diagnosed with ET. Additionally, a small group of study subjects will undergo a 30-60 minute tremor analysis to confirm the neurologist's diagnosis. This is a procedure that is very similar to an electromyogram (EMG) which is used routinely for neurological diagnosis. It involves the use of (1) a device called an accelerometer, which when placed on an individual's finger or hand, can precisely measure the strength of muscle contractions. In addition, if a family is identified with three or more affected individuals, blood specimens will be collected by venipuncture in order to try to localize the gene for ET in the future. Finally, some individuals with essential tremor will undergo the same evaluation (questionnaire and videotaped examination) once per year to see if their tremor progresses.